http://www.ck12.org Chapter 2. Numbers, Not Adjectives
on the land, and they can’t see under the sea, so objections to the visual impact of tide turbines should be less strong
than the objections to wind turbines.
Mythconceptions
Tidal power, while clean and green, should not be called renewable. Extracting power from the tides slows down
the earth’s rotation. We definitely can’t use tidal power long-term.
False.The natural tides already slow down the earth’s rotation. The natural rotational energy loss is roughly 3 TW
(Shepherd, 2003). Thanks to natural tidal friction, each century, the day gets longer by 2.3 milliseconds. Many tidal
energy extraction systems are just extracting energy that would have been lost anyway in friction. But even if we
doubled the power extracted from the earth–moon system, tidal energy would still last more than a billion years.
Figure 14.10:Tide.